Micro LED epitaxial wafer and preparation method thereof, Micro LED chip

Abstract

The present invention relates to the field of optoelectronic technology, and discloses a Micro LED epitaxial wafer and a preparation method thereof, and a Micro LED chip. The Micro LED epitaxial wafer comprises a substrate, on which a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer are sequentially arranged; the first multi-quantum well layer comprises at least one group of first InGaN quantum well layers, first AlGaN / GaN superlattice layers, and first GaN quantum barrier layers stacked sequentially, the second multi-quantum well layer comprises at least one group of second InGaN quantum well layers, second AlGaN / GaN superlattice layers, and second GaN quantum barrier layers stacked sequentially, and the third multi-quantum well layer comprises at least one group of third InGaN quantum well layers, hole injection layers, and third GaN quantum barrier layers stacked sequentially. The Micro LED epitaxial wafer provided by the present invention can improve the light efficiency of the Micro LED chip at a low operating current density.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technology, and in particular to a Micro LED epitaxial wafer and a preparation method thereof, and a Micro LED chip. Background Art

[0002] The development of Micro LED faces challenges in manufacturing technology and materials. For example, as the chip size decreases, the peak EQE of the device decreases and the corresponding current density increases. The efficiency of Micro LED with an operating current density of 0.01A / cm²~0.5A / cm² is still obviously insufficient. In fact, even conventional-sized chips for general lighting and backlight display applications have relatively low efficiency at this current density. The reason is that in order to balance efficiency and cost factors, the operating current density of conventional-sized chips is 20A / cm². 2 Up to 40A / cm 2 The goal of the corresponding epitaxial structure design and material growth is to improve the efficiency under high current density, and its peak EQE is usually in the current density range of 1A / cm²~4A / cm², without paying attention to the device efficiency under low current density. Under different current densities, the dominant reasons for the light-emitting mechanism of LED devices are different, and the corresponding epitaxial layer structure should also change. For example, at the low current density of 0.01A / cm²~0.5A / cm² in the Micro LED working range, the carrier concentration in the quantum well is relatively low, the proportion of Auger recombination is small, and the corresponding quantum well recombination volume can be reduced, which can reduce the number of quantum wells and the number of defects, and improve the EQE of the device under low current density; at the same time, electron leakage has not occurred or the proportion is very low under low current density, and the electron blocking layer structure not only has no effect of blocking electrons, but will block the injection of holes, reducing the quantum efficiency of the device. Therefore, in-depth mechanism research, design and growth of LED epitaxial layer structure under low current density working conditions of Micro LED is a necessary key technology for the research and development of high-efficiency Micro LED devices driven by low working current density. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a Micro LED epitaxial wafer, which improves the light efficiency of the Micro LED chip.

[0004] The technical problem to be solved by the present invention is also to provide a method for preparing a Micro LED epitaxial wafer, which has a simple process and can stably produce a Micro LED epitaxial wafer with good luminescence performance.

[0005] The technical problem to be solved by the present invention is also to provide a Micro LED chip that can improve the light efficiency.

[0006] In order to solve the above technical problems, the present invention provides a Micro LED epitaxial wafer, comprising a substrate, on which a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer are sequentially provided;

[0007] The multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes at least one group of a first InGaN quantum well layer, a first AlGaN / GaN superlattice layer and a first GaN quantum barrier layer stacked in sequence, the second multi-quantum well layer includes at least one group of a second InGaN quantum well layer, a second AlGaN / GaN superlattice layer and a second GaN quantum barrier layer stacked in sequence, the third multi-quantum well layer includes at least one group of a third InGaN quantum well layer, a hole injection layer and a third GaN quantum barrier layer stacked in sequence, the hole injection layer includes a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence, and Si is doped in both the first AlGaN / GaN superlattice layer and the second AlGaN / GaN superlattice layer.

[0008] In some embodiments, the first multi-quantum well layer includes 2 to 5 groups of first InGaN quantum well layers, first AlGaN / GaN superlattice layers, and first GaN quantum barrier layers stacked in sequence;

[0009] The thickness of the first InGaN quantum well layer is 2.15nm~4.5nm;

[0010] The In component content of the first InGaN quantum well layer is 0.07-0.29;

[0011] The thickness of the first GaN quantum barrier layer is 5.3nm~12.7nm;

[0012] The first GaN quantum barrier layer is a Si-doped GaN layer, and its Si doping concentration is 1.9×10 17 atoms / cm 3 ~8.5×10 17 atoms / cm 3 .

[0013] In some embodiments, the first AlGaN / GaN superlattice layer includes 2 to 5 groups of third AlGaN layers and first GaN layers that are alternately stacked;

[0014] The thickness of the third AlGaN layer is 0.3nm-1.2nm;

[0015] The Al component content of the third AlGaN layer is 0.03-0.25;

[0016] The third AlGaN layer is not intentionally doped;

[0017] The first GaN layer is a Si-doped GaN layer, and its Si doping concentration is 2.65×10 17 atoms / cm 3 ~9.7×10 17 atoms / cm 3 ;

[0018] The thickness of the first GaN layer is 0.5 nm to 2 nm.

[0019] In some embodiments, the second multi-quantum well layer includes 2 to 7 groups of second InGaN quantum well layers, second AlGaN / GaN superlattice layers, and second GaN quantum barrier layers stacked in sequence;

[0020] The thickness of the second InGaN quantum well layer is 2.15nm~4.5nm;

[0021] The In component content of the second InGaN quantum well layer is 0.1-0.38;

[0022] The thickness of the second GaN quantum barrier layer is 5.3nm~12.7nm;

[0023] The second GaN quantum barrier layer is a Si-doped GaN layer with a Si doping concentration of 1.2×10 17 atoms / cm 3 ~6.3×10 17 atoms / cm 3 .

[0024] In some embodiments, the second AlGaN / GaN superlattice layer includes 2 to 5 groups of fourth AlGaN layers and second GaN layers stacked alternately;

[0025] The thickness of the fourth AlGaN layer is 0.3nm-1.2nm;

[0026] The Al component content of the fourth AlGaN layer is 0.01-0.18;

[0027] The fourth AlGaN layer is not intentionally doped;

[0028] The second GaN layer is a Si-doped GaN layer, and its Si doping concentration is 2.15×10 17 atoms / cm 3 ~7.2×10 17 atoms / cm 3 ;

[0029] The thickness of the second GaN layer is 0.5 nm to 2 nm.

[0030] In some embodiments, the third multi-quantum well layer includes 1 to 3 groups of a third InGaN quantum well layer, a hole injection layer, and a third GaN quantum barrier layer stacked in sequence;

[0031] The thickness of the third InGaN quantum well layer is 2.15nm~4.5nm;

[0032] The In component content of the third InGaN quantum well layer is 0.05-0.26;

[0033] The thickness of the third GaN quantum barrier layer is 5.3nm-12.7nm;

[0034] The third GaN quantum barrier layer is not intentionally doped.

[0035] In some embodiments, the first AlGaN layer is not intentionally doped;

[0036] The Al component content of the first AlGaN layer is 0.03-0.2;

[0037] The thickness of the first AlGaN layer is 0.5 nm to 2 nm;

[0038] The second AlGaN layer is not intentionally doped;

[0039] The Al component content of the second AlGaN layer is 0.03-0.2;

[0040] The thickness of the second AlGaN layer is 0.5 nm to 2 nm.

[0041] In some embodiments, the thickness of the Mg-doped AlInGaN layer is 1 nm to 7 nm;

[0042] The Al component content of the Mg-doped AlInGaN layer is 0.01-0.1, and the In component content is 0.03-0.15;

[0043] The Mg doping concentration of the Mg-doped AlInGaN layer is 3.5×10 18 atoms / cm 3 ~8.2×10 19 atoms / cm 3 .

[0044] In order to solve the above problems, the present invention also provides a method for preparing a Micro LED epitaxial wafer, comprising the following steps:

[0045] S1. providing a substrate;

[0046] S2, depositing a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer on the substrate in sequence;

[0047] The multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes at least one group of a first InGaN quantum well layer, a first AlGaN / GaN superlattice layer and a first GaN quantum barrier layer stacked in sequence, the second multi-quantum well layer includes at least one group of a second InGaN quantum well layer, a second AlGaN / GaN superlattice layer and a second GaN quantum barrier layer stacked in sequence, the third multi-quantum well layer includes at least one group of a third InGaN quantum well layer, a hole injection layer and a third GaN quantum barrier layer stacked in sequence, the hole injection layer includes a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence, and Si is doped in both the first AlGaN / GaN superlattice layer and the second AlGaN / GaN superlattice layer.

[0048] In some embodiments, after the first multi-quantum well layer is grown, a first annealing treatment is performed on the surface, and the first annealing treatment includes:

[0049] The temperature of the reaction chamber is maintained at 810°C to 1050°C, the growth pressure is maintained at 30 torr to 360 torr, and a mixed gas of N2 and H2 is introduced into the reaction chamber and maintained for 6s to 60s to complete the first operation;

[0050] Stop introducing the N2 and H2 mixed gas to complete the second operation;

[0051] The first operation and the second operation are alternately completed at least once to complete the first annealing treatment.

[0052] In some embodiments, after the third multi-quantum well layer is grown, a second annealing treatment is performed on the surface, and the second annealing treatment includes:

[0053] The temperature of the reaction chamber is maintained at 810°C to 1050°C, the growth pressure is 30 torr to 360 torr, and a mixed gas of N2 and H2 is introduced into the reaction chamber and maintained for 9s to 90s to complete the third operation;

[0054] Stop introducing the N2 and H2 mixed gas to complete the fourth operation;

[0055] The third operation and the fourth operation are alternately completed at least once to complete the second annealing treatment.

[0056] The present invention also provides a Micro LED chip, which includes the Micro LED epitaxial wafer as described above.

[0057] The implementation of the present invention has the following beneficial effects:

[0058] In the Micro LED epitaxial wafer provided by the present invention, the multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes at least one group of first InGaN quantum well layer, first AlGaN / GaN superlattice layer and first GaN quantum barrier layer stacked in sequence, the second multi-quantum well layer includes at least one group of second InGaN quantum well layer, second AlGaN / GaN superlattice layer and second GaN quantum barrier layer stacked in sequence, the third multi-quantum well layer includes at least one group of third InGaN quantum well layer, hole injection layer and third GaN quantum barrier layer stacked in sequence, the hole injection layer includes a first AlGaN layer, Mg-doped AlInGaN layer and second AlGaN layer stacked in sequence. In the present invention, the second multi-quantum well layer is the main light-emitting quantum well region, the first multi-quantum well layer and the third multi-quantum well layer respectively provide part of the electrons and holes to the second multi-quantum well layer to participate in the radiation recombination luminescence, so as to improve the matching degree of the electron-hole concentration in the light-emitting quantum well region and improve the light efficiency of the Micro LED at low working current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 A schematic diagram of the structure of a Micro LED epitaxial wafer provided by the present invention;

[0060] Figure 2 A schematic diagram of the structure of the first multi-quantum well layer of the Micro LED epitaxial wafer provided by the present invention;

[0061] Figure 3 A schematic diagram of the structure of the second multi-quantum well layer of the Micro LED epitaxial wafer provided by the present invention;

[0062] Figure 4 This is a schematic diagram of the structure of the third multi-quantum well layer of the Micro LED epitaxial wafer provided by the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0064] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0065] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0066] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0067] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0068] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the examples of various specific processes and materials provided by the present invention, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0069] In the present invention, "preferred" and "better" are only used to describe implementation methods or embodiments with better effects, and it should be understood that they do not constitute a limitation on the scope of protection of the present invention. In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features. In the present invention, when involving numerical ranges, unless otherwise specified, the two endpoints of the numerical range are included.

[0070] To solve the above problems, the present invention provides a Micro LED epitaxial wafer, such as Figure 1 As shown, it includes a substrate 100, on which a buffer layer 200, an N-type GaN layer 300, a multi-quantum well layer 400, and a P-type GaN layer 500 are sequentially arranged;

[0071] The multi-quantum well layer 400 includes a first multi-quantum well layer 410, a second multi-quantum well layer 420 and a third multi-quantum well layer 430 stacked in sequence, wherein the first multi-quantum well layer 410 includes at least one group of first InGaN quantum well layers 411, first AlGaN / GaN superlattice layers 412 and first GaN quantum barrier layers 413 stacked in sequence, and the second multi-quantum well layer 420 includes at least one group of second InGaN quantum well layers 421, second AlGaN / GaN superlattice layers 422 and second GaN quantum barrier layers 413 stacked in sequence. GaN quantum barrier layer 423, the third multi-quantum well layer 430 includes at least one group of a third InGaN quantum well layer 431, a hole injection layer 432 and a third GaN quantum barrier layer 433 stacked in sequence, the hole injection layer 432 includes a first AlGaN layer 432a, a Mg-doped AlInGaN layer 432b and a second AlGaN layer 432c stacked in sequence, and the first AlGaN / GaN superlattice layer 412 and the second AlGaN / GaN superlattice layer 422 are both doped with Si.

[0072] In the present invention, the second multi-quantum well layer is the main light-emitting quantum well region, and the first multi-quantum well layer and the third multi-quantum well layer respectively provide part of the electrons and holes to the second multi-quantum well layer to participate in radiative recombination luminescence, so as to improve the matching degree of the electron-hole concentration in the light-emitting quantum well region and improve the light efficiency of the Micro LED at low operating current density.

[0073] In some embodiments, the emission wavelength of the second multi-quantum well layer is greater than the emission wavelength of the first multi-quantum well layer, the emission wavelength of the second multi-quantum well layer is greater than the emission wavelength of the third multi-quantum well layer, and the second multi-quantum well layer is the main light-emitting layer. Preferably, the emission wavelength range of the first multi-quantum well layer is 425nm~460nm; the emission wavelength range of the second multi-quantum well layer is 465nm~485nm; the emission wavelength range of the third multi-quantum well layer is 420nm~454nm. The quantum well layers of the multi-quantum well layer form a change in which the emission wavelength first increases and then decreases. This structure can reduce the lattice mismatch stress between the multi-quantum well layers, reduce the defects caused by the large mismatch stress, improve the quality of the main light-emitting quantum well region at low working current density, and thus improve the radiation recombination efficiency of the multi-quantum well layer.

[0074] Specifically, the specific structure of the multi-quantum well layer 400 is as follows.

[0075] (i) The first multi-quantum well layer 410 has a structure as follows: Figure 2 shown.

[0076] In some embodiments, the first multi-quantum well layer 410 includes 2 to 5 groups of first InGaN quantum well layers 411 , first AlGaN / GaN superlattice layers 412 , and first GaN quantum barrier layers 413 stacked in sequence.

[0077] In some embodiments, the thickness of the first InGaN quantum well layer 411 is 2.15 nm to 4.5 nm, and exemplary thicknesses thereof are 2.5 nm, 3 nm, 3.5 nm, and 4 nm, but are not limited to the above examples.

[0078] In some embodiments, the In component content of the first InGaN quantum well layer 411 is 0.07-0.29, and its exemplary In component content is 0.1, 0.13, 0.15, 0.18, 0.2, 0.25, 0.28, not limited to the above. Preferably, the In component content of the first InGaN quantum well layer 411 is less than the In component content of the second InGaN quantum well layer 421, which helps to achieve the emission wavelength of the second multi-quantum well layer> the emission wavelength of the first multi-quantum well layer, the emission wavelength of the second multi-quantum well layer> the emission wavelength of the third multi-quantum well layer, and the second multi-quantum well layer is the main light-emitting layer. The quantum well layer of the multi-quantum well layer forms a change in which the emission wavelength first increases and then decreases. This structure can reduce the lattice mismatch stress between the multi-quantum well layers, reduce the defects caused by the large mismatch stress, improve the quality of the main light-emitting quantum well region at low working current density, and thus improve the radiation recombination efficiency of the multi-quantum well layer.

[0079] In some embodiments, the first AlGaN / GaN superlattice layer 412 includes 2 to 5 groups of third AlGaN layers and first GaN layers that are alternately stacked.

[0080] In some embodiments, the third AlGaN layer is not intentionally doped; the thickness of the third AlGaN layer is 0.3 nm to 1.2 nm, and its exemplary thickness is 0.5 nm, 0.8 nm, 1 nm, and 1.1 nm, but is not limited to the above list.

[0081] In some embodiments, the Al component content of the third AlGaN layer is 0.03-0.25, and exemplary Al component contents are 0.05, 0.1, 0.15, and 2, but are not limited to the above list.

[0082] In some embodiments, the first GaN layer is a Si-doped GaN layer, and the Si doping concentration is 2.65×10 17 atoms / cm 3 ~9.7×10 17 atoms / cm 3 , with an exemplary Si doping concentration of 3×10 17 atoms / cm 3 , 6×10 17 atoms / cm 3 ,9×10 17 atoms / cm 3 , but not limited to the above listed.

[0083] In some embodiments, the thickness of the first GaN layer is 0.5 nm to 2 nm, and exemplary thicknesses thereof are 0.6 nm, 0.8 nm, 1 nm, 1.3 nm, 1.6 nm, and 1.9 nm, but are not limited to the above list.

[0084] The first AlGaN / GaN superlattice layer 412 is an electron injection insertion layer, which is an AlGaN / GaN superlattice structure material with a high Al component, and the GaN layer is doped with Si elements. On the one hand, the first AlGaN / GaN superlattice layer 412 can provide some electrons. On the other hand, it helps to reduce the blocking effect of the second GaN quantum barrier layer and the third GaN quantum barrier layer on the hole injection of the P-type GaN layer, increase the hole concentration injected from the P-type GaN layer to the second multi-quantum well layer, significantly improve the matching degree of the electron hole concentration in the light-emitting quantum well region, and improve the light efficiency of the Micro LED at low operating current density.

[0085] In some embodiments, the thickness of the first GaN quantum barrier layer 413 is 5.3 nm to 12.7 nm, and exemplary thicknesses thereof are 6 nm, 7.8 nm, 10 nm, and 11.1 nm, but are not limited to the above examples.

[0086] In some embodiments, the first GaN quantum barrier layer 413 is a Si-doped GaN layer, and the Si doping concentration is 1.9×10 17 atoms / cm 3 ~8.5×10 17 atoms / cm 3 , with an exemplary Si doping concentration of 3×10 17 atoms / cm 3 , 6×10 17 atoms / cm 3 , 7.5×10 17 atoms / cm 3 , but not limited to the above listed.

[0087] (ii) The second multi-quantum well layer 420 has a structure as follows: Figure 3 shown.

[0088] In some embodiments, the second multi-quantum well layer 420 includes 2 to 7 groups of second InGaN quantum well layers 421 , second AlGaN / GaN superlattice layers 422 , and second GaN quantum barrier layers 423 stacked in sequence.

[0089] In some embodiments, the thickness of the second InGaN quantum well layer 421 is 2.15 nm to 4.5 nm, and exemplary thicknesses thereof are 2.5 nm, 3 nm, 3.5 nm, and 4 nm, but are not limited to the above examples.

[0090] In some embodiments, the In component content of the second InGaN quantum well layer 421 is 0.1-0.38, and its exemplary In component content is 0.15, 0.18, 0.21, 0.25, 0.28, 0.3, 0.35, not limited to the above. Preferably, the In component content of the first InGaN quantum well layer 411 is less than the In component content of the second InGaN quantum well layer 421, and the In component content of the third InGaN quantum well layer 431 is less than the In component content of the second InGaN quantum well layer 421, which helps to achieve the emission wavelength of the second multi-quantum well layer> the emission wavelength of the first multi-quantum well layer, the emission wavelength of the second multi-quantum well layer> the emission wavelength of the third multi-quantum well layer, and the second multi-quantum well layer is the main light-emitting layer. The quantum well layers of the multi-quantum well layer form a change in which the light-emitting wavelength first increases and then decreases. This structure can reduce the lattice mismatch stress between the multi-quantum well layers, reduce the defects caused by large mismatch stress, and improve the quality of the main light-emitting quantum well region under low operating current density, thereby improving the radiation recombination efficiency of the multi-quantum well layer.

[0091] In some embodiments, the second AlGaN / GaN superlattice layer 422 includes 2 to 5 groups of fourth AlGaN layers and second GaN layers that are alternately stacked.

[0092] In some embodiments, the fourth AlGaN layer is not intentionally doped; the thickness of the fourth AlGaN layer is 0.3 nm to 1.2 nm, and exemplary thicknesses thereof are 0.5 nm, 0.8 nm, 1 nm, and 1.1 nm, but are not limited to the above examples.

[0093] In some embodiments, the Al component content of the fourth AlGaN layer is 0.01-0.18; exemplary Al component contents are 0.05, 0.1, 0.15, and 0.07, but are not limited to the above list.

[0094] In some embodiments, the second GaN layer is a Si-doped GaN layer, and the Si doping concentration is 2.15×10 17 atoms / cm 3 ~7.2×10 17 atoms / cm 3 , with an exemplary Si doping concentration of 3.5×10 17 atoms / cm 3 , 6.7×10 17 atoms / cm 3 ,7×10 17 atoms / cm 3 , but not limited to the above listed.

[0095] In some embodiments, the thickness of the second GaN layer is 0.5 nm to 2 nm, and exemplary thicknesses thereof are 0.8 nm, 1 nm, 1.5 nm, and 1.9 nm, but are not limited to the above examples.

[0096] The second AlGaN / GaN superlattice layer 422 is an electron injection insertion layer, which is an AlGaN / GaN superlattice structure material with a low Al component, and the GaN is low-doped with Si elements. On the one hand, the second AlGaN / GaN superlattice layer 422 can provide some electrons. On the other hand, the quantum barrier layer close to the P-type GaN layer adopts a low Al component structural design, which helps to reduce the blocking effect of the second GaN quantum barrier layer and the third GaN quantum barrier layer on the hole injection of the P-type GaN layer, increase the hole concentration injected from the P-type GaN layer to the second multi-quantum well layer, significantly improve the matching degree of the electron hole concentration in the light-emitting quantum well region, and improve the light efficiency of the Micro LED at a low operating current density.

[0097] In some embodiments, the thickness of the second GaN quantum barrier layer 423 is 5.3 nm to 12.7 nm, and exemplary thicknesses thereof are 6 nm, 7.8 nm, 10 nm, and 11.1 nm, but are not limited to the above examples.

[0098] In some embodiments, the second GaN quantum barrier layer 423 is a Si-doped GaN layer, and the Si doping concentration is 1.2×10 17 atoms / cm 3 ~6.3×10 17 atoms / cm 3 , with an exemplary Si doping concentration of 2×10 17 atoms / cm 3 , 4×10 17 atoms / cm 3 , 6×10 17 atoms / cm 3 , but not limited to the above listed.

[0099] (iii) The third multi-quantum well layer 430 has a structure as follows: Figure 4 shown.

[0100] In some embodiments, the third multi-quantum well layer 430 includes 1 to 3 groups of a third InGaN quantum well layer 431 , a hole injection layer 432 , and a third GaN quantum barrier layer 433 which are stacked in sequence.

[0101] In some embodiments, the thickness of the third InGaN quantum well layer 431 is 2.15 nm to 4.5 nm, and exemplary thicknesses thereof are 2.5 nm, 3 nm, 3.5 nm, and 4 nm, but are not limited to the above examples.

[0102] In some embodiments, the In component content of the third InGaN quantum well layer 431 is 0.05-0.26, and its exemplary In component content is 0.1, 0.13, 0.15, 0.18, 0.2, 0.25, not limited to the above. Preferably, the In component content of the third InGaN quantum well layer 431 is less than the In component content of the second InGaN quantum well layer 421, which helps to achieve the emission wavelength of the second multi-quantum well layer> the emission wavelength of the first multi-quantum well layer, the emission wavelength of the second multi-quantum well layer> the emission wavelength of the third multi-quantum well layer, and the second multi-quantum well layer is the main light-emitting layer. The quantum well layer of the multi-quantum well layer forms a change in which the emission wavelength first increases and then decreases. This structure can reduce the lattice mismatch stress between the multi-quantum well layers, reduce the defects caused by the large mismatch stress, improve the quality of the main light-emitting quantum well region at low working current density, and thus improve the radiation recombination efficiency of the multi-quantum well layer.

[0103] The hole injection layer 432 includes a first AlGaN layer 432a, a Mg-doped AlInGaN layer 432b, and a second AlGaN layer 432c stacked in sequence. The first AlGaN layer 432a is a front hole injection protection layer, the Mg-doped AlInGaN layer 432b is a hole injection enhancement layer, and the second AlGaN layer 432c is a rear hole injection protection layer, wherein the front hole injection protection layer and the rear hole injection protection layer are both made of AlGaN material with a low Al component, and the hole injection enhancement layer is made of AlGaInN material doped with Mg element, and the specific configuration is as follows:

[0104] In some embodiments, the first AlGaN layer 432a is not intentionally doped; the Al component content of the first AlGaN layer 432a is 0.03-0.2, and its exemplary Al component content is 0.05, 0.1, 0.15, 0.2, but is not limited to the above list.

[0105] In some embodiments, the thickness of the first AlGaN layer 432 a is 0.5 nm to 2 nm, and exemplary thicknesses thereof are 0.6 nm, 0.9 nm, 1.2 nm, and 1.5 nm, but are not limited to the above examples.

[0106] In some embodiments, the Mg-doped AlInGaN layer 432 b has a thickness of 1 nm to 7 nm, and exemplary thicknesses thereof are 2 nm, 4 nm, 5 nm, and 6 nm, but are not limited to the above examples.

[0107] In some embodiments, the Mg-doped AlInGaN layer 432 b has an Al component content of 0.01-0.1, and an In component content of 0.03-0.15.

[0108] In some embodiments, the Mg doping concentration of the Mg-doped AlInGaN layer 432 b is 3.5×10 18 atoms / cm 3 ~8.2×10 19 atoms / cm 3 , with an exemplary Mg doping concentration of 4×10 18 atoms / cm 3 , 8×10 18 atoms / cm 3 , 5×10 19 atoms / cm 3 , but not limited to the above listed.

[0109] In some embodiments, the second AlGaN layer 432c is not intentionally doped; the Al component content of the second AlGaN layer 432c is 0.03-0.2, and its exemplary Al component content is 0.05, 0.1, 0.15, 0.2, not limited to the above list.

[0110] In some embodiments, the thickness of the second AlGaN layer 432 c is 0.5 nm to 2 nm, and exemplary thicknesses thereof are 0.6 nm, 0.9 nm, 1.2 nm, and 1.5 nm, but are not limited to the above examples.

[0111] The hole injection layer 432 can provide some holes on the one hand. On the other hand, it helps to reduce the blocking effect of the second GaN quantum barrier layer and the third GaN quantum barrier layer on the hole injection of the P-type GaN layer, increase the hole concentration injected from the P-type GaN layer to the second multi-quantum well layer, significantly improve the matching degree of the electron-hole concentration in the light-emitting quantum well region, and improve the light efficiency of the MicroLED at low operating current density.

[0112] In some embodiments, the thickness of the third GaN quantum barrier layer 433 is 5.3 nm to 12.7 nm, and exemplary thicknesses thereof are 6 nm, 7.8 nm, 10 nm, and 11.1 nm, but are not limited to the above examples. The third GaN quantum barrier layer 433 is not intentionally doped.

[0113] Accordingly, the present invention provides a method for preparing a Micro LED epitaxial wafer, comprising the following steps:

[0114] S1, providing a substrate 100;

[0115] In some embodiments, the substrate 100 may be selected from one of a sapphire substrate, a SiO2 sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a zinc oxide substrate. Preferably, the substrate 100 is a sapphire substrate, which is a commonly used GaN-based LED substrate material. The sapphire substrate has a mature preparation process, a low price, is easy to clean and handle, and has good stability at high temperatures.

[0116] S2, sequentially depositing a buffer layer 200, an N-type GaN layer 300, a multi-quantum well layer 400, and a P-type GaN layer 500 on the substrate 100;

[0117] The multi-quantum well layer 400 includes a first multi-quantum well layer 410, a second multi-quantum well layer 420 and a third multi-quantum well layer 430 stacked in sequence, the first multi-quantum well layer 410 includes at least one group of first InGaN quantum well layer 411, first AlGaN / GaN superlattice layer 412 and first GaN quantum barrier layer 413 stacked in sequence, the second multi-quantum well layer 420 includes at least one group of second InGaN quantum well layer 421, second AlGaN / GaN superlattice layer 422 and second GaN quantum barrier layer 423 stacked in sequence, the third multi-quantum well layer 430 includes at least one group of third InGaN quantum well layer 431, hole injection layer 432 and third GaN quantum barrier layer 433 stacked in sequence, the hole injection layer 432 includes a first AlGaN layer 432a, a Mg-doped AlInGaN layer 432b and a second AlGaN layer 432c stacked in sequence.

[0118] Specifically, the above step S2 specifically includes the following steps:

[0119] S21 , depositing the buffer layer 200 on the substrate 100 .

[0120] In some embodiments, an AlN buffer layer is deposited during PVD. The AlN buffer layer provides nucleation centers with the same orientation as the substrate, releases the stress caused by the lattice mismatch between GaN and the substrate and the thermal stress caused by the mismatch in thermal expansion coefficients, provides a flat nucleation surface for further growth, reduces the contact angle of nucleation growth, and enables the island-like grown GaN grains to be connected into a surface within a smaller thickness, thereby transforming into two-dimensional epitaxial growth.

[0121] S22 , depositing the N-type GaN layer 300 on the buffer layer 200 .

[0122] In some embodiments, the temperature of the reaction chamber is controlled at 1050° C. to 1200° C., the pressure is controlled at 100 torr to 600 torr, and an N source, a Ga source, and a Si source are introduced to grow the N-type GaN layer.

[0123] S23 , depositing the multi-quantum well layer 400 on the N-type GaN layer 300 .

[0124] In some embodiments, the multi-quantum well layer is prepared by the following method:

[0125] The first multi-quantum well layer 410 , the second multi-quantum well layer 420 , and the third multi-quantum well layer 430 are grown in sequence to obtain a multi-quantum well layer.

[0126] (i) In some embodiments, the first multi-quantum well layer 410 is prepared by the following method:

[0127] At least one set of a first InGaN quantum well layer 411 , a first AlGaN / GaN superlattice layer 412 , and a first GaN quantum barrier layer 413 stacked in sequence is grown.

[0128] In some embodiments, the first InGaN quantum well layer 411 is made by the following method:

[0129] The growth temperature of the reaction chamber is maintained at 678° C. to 916° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and In source are introduced to grow the first InGaN quantum well layer.

[0130] In some embodiments, the first AlGaN / GaN superlattice layer 412 is manufactured by the following method:

[0131] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Al source are introduced to grow the third AlGaN layer;

[0132] The growth temperature of the reaction chamber is maintained at 820°C to 918°C, the growth pressure is 30 torr to 360 torr, and N source, Ga source, and Si source are introduced to grow the first GaN layer;

[0133] The third AlGaN layer and the first GaN layer are grown alternately to obtain a first AlGaN / GaN superlattice layer 412 .

[0134] In some embodiments, the first GaN quantum barrier layer 413 is prepared by the following method:

[0135] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Si source are introduced to grow the first GaN quantum barrier layer.

[0136] (ii) In some embodiments, the second multi-quantum well layer 420 is prepared by the following method:

[0137] At least one set of a second InGaN quantum well layer 421 , a second AlGaN / GaN superlattice layer 422 , and a second GaN quantum barrier layer 423 stacked in sequence is grown.

[0138] In some embodiments, the second InGaN quantum well layer 421 is made by the following method:

[0139] The growth temperature of the reaction chamber is maintained at 678° C. to 916° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and In source are introduced to grow a second InGaN quantum well layer.

[0140] In some embodiments, the second AlGaN / GaN superlattice layer 422 is made by the following method:

[0141] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Al source are introduced to grow a fourth AlGaN layer;

[0142] The growth temperature of the reaction chamber is maintained at 820°C to 918°C, the growth pressure is 30 torr to 360 torr, and N source, Ga source, and Si source are introduced to grow the second GaN layer;

[0143] The fourth AlGaN layer and the second GaN layer are grown alternately to obtain a second AlGaN / GaN superlattice layer.

[0144] In some embodiments, the second GaN quantum barrier layer 423 is prepared by the following method:

[0145] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Si source are introduced to grow a second GaN quantum barrier layer.

[0146] (III) In some embodiments, the third multi-quantum well layer 430 is prepared by the following method:

[0147] At least one set of sequentially stacked third InGaN quantum well layer 431 , hole injection layer 432 , and third GaN quantum barrier layer 433 is periodically grown.

[0148] In some embodiments, the third InGaN quantum well layer 431 is prepared by the following method:

[0149] The growth temperature of the reaction chamber is maintained at 678° C. to 916° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and In source are introduced to grow the third InGaN quantum well layer.

[0150] In some embodiments, the hole injection layer 432 is prepared by the following method:

[0151] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Al source are introduced to grow the first AlGaN layer;

[0152] The growth temperature of the reaction chamber is maintained at 820°C to 918°C, the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, Al source, In source, and Mg source are introduced to grow an AlInGaN layer;

[0153] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Al source are introduced to grow the second AlGaN layer.

[0154] In some embodiments, the third GaN quantum barrier layer 433 is prepared by the following method:

[0155] The growth temperature of the reaction chamber is maintained at 820° C. to 918° C., the growth pressure is maintained at 30 torr to 360 torr, and N source, Ga source, and Si source are introduced to grow the third GaN quantum barrier layer.

[0156] In some embodiments, after the first multi-quantum well layer is grown, a first annealing treatment is performed on the surface, and the first annealing treatment includes:

[0157] The temperature of the reaction chamber is maintained at 810°C to 1050°C, the growth pressure is maintained at 30 torr to 360 torr, and a mixed gas of N2 and H2 is introduced into the reaction chamber and maintained for 6s to 60s to complete the first operation;

[0158] Stop introducing the N2 and H2 mixed gas to complete the second operation;

[0159] The first operation and the second operation are alternately completed at least once to complete the first annealing treatment.

[0160] After the deposition of the first multi-quantum well layer is completed, a first annealing treatment is performed to decompose defects such as materials with poor surface crystallization quality and In clusters with a high In component, which is beneficial to improving the crystal quality of the material. At the same time, a slightly rough material surface is formed, which can reduce the in-plane total reflection and light absorption loss of photons in the semiconductor material and improve the light extraction efficiency.

[0161] Further, in some embodiments, after the third multi-quantum well layer is grown, a second annealing treatment is performed on the surface, and the second annealing treatment includes:

[0162] The temperature of the reaction chamber is maintained at 810°C to 1050°C, the growth pressure is 30 torr to 360 torr, and a mixed gas of N2 and H2 is introduced into the reaction chamber and maintained for 9s to 90s to complete the third operation;

[0163] Stop introducing the N2 and H2 mixed gas to complete the fourth operation;

[0164] The third operation and the fourth operation are alternately completed at least once to complete the second annealing treatment.

[0165] After the deposition of the third multi-quantum well layer is completed, a second annealing treatment is performed to decompose defects such as materials with poor surface crystallization quality and clusters of In with a high In component, which is beneficial to improving the crystal quality of the material. At the same time, a slightly rough material surface is formed, which can reduce the in-plane total reflection and light absorption loss of photons in the semiconductor material and improve the light extraction efficiency.

[0166] S24 , depositing the P-type GaN layer 500 on the multi-quantum well layer 400 .

[0167] In some embodiments, the temperature of the reaction chamber is controlled at 900° C. to 1050° C., the pressure is controlled at 100 torr to 600 torr, and an N source, a Mg source, and a Ga source are introduced to grow the P-type GaN layer.

[0168] Accordingly, the present invention also provides a Micro LED chip, which includes the above-mentioned Micro LED epitaxial wafer. Micro LED epitaxial wafer is the basic material for the manufacture of Micro LED chips, and the quality and characteristics of Micro LED epitaxial wafer directly affect the performance and yield of the final Micro LED chip.

[0169] The present invention is further described below with specific embodiments:

[0170] Example 1

[0171] This embodiment provides a Micro LED epitaxial wafer, including a substrate, on which a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer are sequentially provided;

[0172] The multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes three groups of first InGaN quantum well layers, first AlGaN / GaN superlattice layers and first GaN quantum barrier layers stacked in sequence, the second multi-quantum well layer includes five groups of second InGaN quantum well layers, second AlGaN / GaN superlattice layers and second GaN quantum barrier layers stacked in sequence, the third multi-quantum well layer includes two groups of third InGaN quantum well layers, hole injection layers and third GaN quantum barrier layers stacked in sequence, and the hole injection layer includes a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence.

[0173] The thickness of the first InGaN quantum well layer is 3 nm, and the In component content is 0.14. The thickness of the first GaN quantum barrier layer is 7 nm, and the Si doping concentration is 5×10 17 atoms / cm 3 .

[0174] The first AlGaN / GaN superlattice layer includes three groups of third AlGaN layers and first GaN layers stacked alternately; the thickness of the third AlGaN layer is 1 nm, and the Al component content is 0.15; the thickness of the first GaN layer is 1 nm, and the Si doping concentration is 7×10 17 atoms / cm 3 .

[0175] The thickness of the second InGaN quantum well layer is 3 nm, and the In component content is 0.25; the thickness of the second GaN quantum barrier layer is 7 nm, and the Si doping concentration is 4×10 17 atoms / cm 3 .

[0176] The second AlGaN / GaN superlattice layer includes three groups of alternately stacked fourth AlGaN layers and second GaN layers; the thickness of the fourth AlGaN layer is 0.8 nm, and the Al component content is 0.09; the thickness of the second GaN layer is 1 nm, and the Si doping concentration is 5.5×10 17 atoms / cm 3 .

[0177] The thickness of the third InGaN quantum well layer is 3 nm, and the In component content is 0.14; the thickness of the third GaN quantum barrier layer is 7 nm, and no intentional doping is performed.

[0178] The first AlGaN layer is not intentionally doped, has an Al component content of 0.11, and a thickness of 0.12 nm;

[0179] The second AlGaN layer is not intentionally doped, has an Al composition content of 0.11, and a thickness of 0.14 nm.

[0180] The thickness of the Mg-doped AlInGaN layer is 4 nm, the Al component content is 0.55, the In component content is 0.09, and the Mg doping concentration is 3.2×10 19 atoms / cm 3 .

[0181] Example 2

[0182] This embodiment provides a Micro LED epitaxial wafer, including a substrate, on which a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer are sequentially provided;

[0183] The multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes three groups of first InGaN quantum well layers, first AlGaN / GaN superlattice layers and first GaN quantum barrier layers stacked in sequence, the second multi-quantum well layer includes five groups of second InGaN quantum well layers, second AlGaN / GaN superlattice layers and second GaN quantum barrier layers stacked in sequence, the third multi-quantum well layer includes two groups of third InGaN quantum well layers, hole injection layers and third GaN quantum barrier layers stacked in sequence, and the hole injection layer includes a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence.

[0184] The thickness of the first InGaN quantum well layer is 3 nm, and the In component content is 0.2. The thickness of the first GaN quantum barrier layer is 7 nm, and the Si doping concentration is 5×10 17 atoms / cm 3 .

[0185] The first AlGaN / GaN superlattice layer includes three groups of third AlGaN layers and first GaN layers stacked alternately; the thickness of the third AlGaN layer is 1 nm, and the Al component content is 0.15; the thickness of the first GaN layer is 1 nm, and the Si doping concentration is 7×10 17 atoms / cm 3 .

[0186] The thickness of the second InGaN quantum well layer is 3 nm, and the In component content is 0.37; the thickness of the second GaN quantum barrier layer is 7 nm, and the Si doping concentration is 4×10 17 atoms / cm 3 .

[0187] The second AlGaN / GaN superlattice layer includes three groups of alternately stacked fourth AlGaN layers and second GaN layers; the thickness of the fourth AlGaN layer is 0.8 nm, and the Al component content is 0.09; the thickness of the second GaN layer is 1 nm, and the Si doping concentration is 5.5×10 17 atoms / cm 3 .

[0188] The thickness of the third InGaN quantum well layer is 3 nm, and the In component content is 0.24; the thickness of the third GaN quantum barrier layer is 7 nm, and no intentional doping is performed.

[0189] The first AlGaN layer is not intentionally doped, the Al content is 0.11, and the thickness is 0.12nm. The second AlGaN layer is not intentionally doped, the Al content is 0.11, and the thickness is 0.14nm. The thickness of the Mg-doped AlInGaN layer is 4nm, the Al content is 0.55, the In content is 0.09, and the Mg doping concentration is 3.2×10 19 atoms / cm 3 .

[0190] Example 3

[0191] This embodiment provides a Micro LED epitaxial wafer, including a substrate, on which a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer are sequentially provided;

[0192] The multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes 4 groups of first InGaN quantum well layers, first AlGaN / GaN superlattice layers and first GaN quantum barrier layers stacked in sequence, the second multi-quantum well layer includes 7 groups of second InGaN quantum well layers, second AlGaN / GaN superlattice layers and second GaN quantum barrier layers stacked in sequence, the third multi-quantum well layer includes 1 group of third InGaN quantum well layers, hole injection layers and third GaN quantum barrier layers stacked in sequence, and the hole injection layer includes a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence.

[0193] The thickness of the first InGaN quantum well layer is 3 nm, and the In component content is 0.14. The thickness of the first GaN quantum barrier layer is 7 nm, and the Si doping concentration is 5×10 17 atoms / cm 3 .

[0194] The first AlGaN / GaN superlattice layer includes three groups of third AlGaN layers and first GaN layers stacked alternately; the thickness of the third AlGaN layer is 1 nm, and the Al component content is 0.15; the thickness of the first GaN layer is 1 nm, and the Si doping concentration is 7×10 17 atoms / cm 3 .

[0195] The thickness of the second InGaN quantum well layer is 3 nm, and the In component content is 0.25; the thickness of the second GaN quantum barrier layer is 7 nm, and the Si doping concentration is 4×10 17 atoms / cm 3 .

[0196] The second AlGaN / GaN superlattice layer includes three groups of alternately stacked fourth AlGaN layers and second GaN layers; the thickness of the fourth AlGaN layer is 0.8 nm, and the Al component content is 0.09; the thickness of the second GaN layer is 1 nm, and the Si doping concentration is 5.5×10 17 atoms / cm 3 .

[0197] The thickness of the third InGaN quantum well layer is 3 nm, and the In component content is 0.14; the thickness of the third GaN quantum barrier layer is 7 nm, and no intentional doping is performed.

[0198] The first AlGaN layer is not intentionally doped, has an Al component content of 0.11, and a thickness of 0.12 nm;

[0199] The second AlGaN layer is not intentionally doped, has an Al composition content of 0.11, and a thickness of 0.14 nm.

[0200] The thickness of the Mg-doped AlInGaN layer is 4 nm, the Al component content is 0.55, the In component content is 0.09, and the Mg doping concentration is 3.2×10 19 atoms / cm 3 .

[0201] Comparative Example 1

[0202] This comparative example provides a Micro LED epitaxial wafer, which is different from Example 1 in that: its multi-quantum well layer includes alternately stacked GaN quantum barrier layers and InGaN quantum well layers, and the rest is the same as Example 1.

[0203] The Micro LED epitaxial wafers prepared in Examples 1 to 3 and Comparative Example 1 were used to prepare Micro LED chips using the same chip process conditions and the luminous efficiency improvement rate relative to Comparative Example 1 was tested. The specific test results are shown in Table 1.

[0204] Table 1 Performance test results of Micro LED chips prepared in Examples 1 to 3 and Comparative Example 1

[0205]

[0206] In the Micro LED epitaxial wafer provided by the present invention, the second multi-quantum well layer is the main light-emitting quantum well region, and the first multi-quantum well layer and the third multi-quantum well layer respectively provide part of the electrons and holes to the second multi-quantum well layer to participate in radiative recombination luminescence, so as to improve the matching degree of the electron-hole concentration in the light-emitting quantum well region and improve the luminous efficiency of the MicroLED at low operating current density.

[0207] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0208] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A Micro LED epitaxial wafer, characterized in that: It comprises a substrate, on which a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer are sequentially arranged; The multi-quantum well layer comprises a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer comprises at least one group of a first InGaN quantum well layer, a first AlGaN / GaN superlattice layer and a first GaN quantum barrier layer stacked in sequence, the second multi-quantum well layer comprises at least one group of a second InGaN quantum well layer, a second AlGaN / GaN superlattice layer and a second GaN quantum barrier layer stacked in sequence, the third multi-quantum well layer comprises at least one group of a third InGaN quantum well layer, a hole injection layer and a third GaN quantum barrier layer stacked in sequence, the hole injection layer comprises a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence, and Si is doped in both the first AlGaN / GaN superlattice layer and the second AlGaN / GaN superlattice layer; The light emission wavelength of the second multi-quantum well layer is greater than the light emission wavelength of the first multi-quantum well layer, and the light emission wavelength of the second multi-quantum well layer is greater than the light emission wavelength of the third multi-quantum well layer; The In component content of the first InGaN quantum well layer is less than the In component content of the second InGaN quantum well layer; The In component content of the first InGaN quantum well layer is less than the In component content of the second InGaN quantum well layer.

2. The Micro LED epitaxial wafer according to claim 1, wherein: The first multi-quantum well layer includes 2 to 5 groups of first InGaN quantum well layers, first AlGaN / GaN superlattice layers and first GaN quantum barrier layers stacked in sequence; The thickness of the first InGaN quantum well layer is 2.15nm~4.5nm; The In component content of the first InGaN quantum well layer is 0.07-0.29; The thickness of the first GaN quantum barrier layer is 5.3nm~12.7nm; The first GaN quantum barrier layer is a Si-doped GaN layer, and its Si doping concentration is 1.9×10 17 atoms / cm 3 ~8.5×10 17 atoms / cm 3 .

3. The Micro LED epitaxial wafer according to claim 1 or 2, wherein: The first AlGaN / GaN superlattice layer includes 2 to 5 groups of third AlGaN layers and first GaN layers that are alternately stacked; The thickness of the third AlGaN layer is 0.3nm-1.2nm; The Al component content of the third AlGaN layer is 0.03-0.25; The third AlGaN layer is not intentionally doped; The first GaN layer is a Si-doped GaN layer, and its Si doping concentration is 2.65×10 17 atoms / cm 3 ~9.7×10 17 atoms / cm 3 ; The thickness of the first GaN layer is 0.5 nm to 2 nm.

4. The Micro LED epitaxial wafer according to claim 1, wherein: The second multi-quantum well layer includes 2 to 7 groups of second InGaN quantum well layers, second AlGaN / GaN superlattice layers and second GaN quantum barrier layers stacked in sequence; The thickness of the second InGaN quantum well layer is 2.15nm~4.5nm; The In component content of the second InGaN quantum well layer is 0.1-0.38; The thickness of the second GaN quantum barrier layer is 5.3nm~12.7nm; The second GaN quantum barrier layer is a Si-doped GaN layer, and its Si doping concentration is 1.2×10 17 atoms / cm 3 ~6.3×10 17 atoms / cm 3 .

5. The Micro LED epitaxial wafer according to claim 1 or 4, wherein: The second AlGaN / GaN superlattice layer includes 2 to 5 groups of fourth AlGaN layers and second GaN layers stacked alternately; The thickness of the fourth AlGaN layer is 0.3nm-1.2nm; The Al component content of the fourth AlGaN layer is 0.01-0.18; The fourth AlGaN layer is not intentionally doped; The second GaN layer is a Si-doped GaN layer, and its Si doping concentration is 2.15×10 17 atoms / cm 3 ~7.2×10 17 atoms / cm 3 ; The thickness of the second GaN layer is 0.5 nm to 2 nm.

6. The Micro LED epitaxial wafer according to claim 1, wherein: The third multi-quantum well layer includes 1 to 3 groups of third InGaN quantum well layers, hole injection layers and third GaN quantum barrier layers stacked in sequence; The thickness of the third InGaN quantum well layer is 2.15nm~4.5nm; The In component content of the third InGaN quantum well layer is 0.05-0.26; The thickness of the third GaN quantum barrier layer is 5.3nm~12.7nm; The third GaN quantum barrier layer is not intentionally doped.

7. The Micro LED epitaxial wafer according to claim 1, wherein: The first AlGaN layer is not intentionally doped; The Al component content of the first AlGaN layer is 0.03-0.2; The thickness of the first AlGaN layer is 0.5 nm to 2 nm; The second AlGaN layer is not intentionally doped; The Al component content of the second AlGaN layer is 0.03-0.2; The thickness of the second AlGaN layer is 0.5 nm to 2 nm.

8. The Micro LED epitaxial wafer according to claim 1, wherein: The thickness of the Mg-doped AlInGaN layer is 1 nm to 7 nm; The Al component content of the Mg-doped AlInGaN layer is 0.01-0.1, and the In component content is 0.03-0.15; The Mg doping concentration of the Mg-doped AlInGaN layer is 3.5×10 18 atoms / cm 3 ~8.2×10 19 atoms / cm 3 .

9. A method for preparing a Micro LED epitaxial wafer according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. providing a substrate; S2, depositing a buffer layer, an N-type GaN layer, a multi-quantum well layer, and a P-type GaN layer on the substrate in sequence; The multi-quantum well layer includes a first multi-quantum well layer, a second multi-quantum well layer and a third multi-quantum well layer stacked in sequence, the first multi-quantum well layer includes at least one group of a first InGaN quantum well layer, a first AlGaN / GaN superlattice layer and a first GaN quantum barrier layer stacked in sequence, the second multi-quantum well layer includes at least one group of a second InGaN quantum well layer, a second AlGaN / GaN superlattice layer and a second GaN quantum barrier layer stacked in sequence, the third multi-quantum well layer includes at least one group of a third InGaN quantum well layer, a hole injection layer and a third GaN quantum barrier layer stacked in sequence, the hole injection layer includes a first AlGaN layer, a Mg-doped AlInGaN layer and a second AlGaN layer stacked in sequence, and Si is doped in both the first AlGaN / GaN superlattice layer and the second AlGaN / GaN superlattice layer.

10. The method for preparing a Micro LED epitaxial wafer according to claim 9, wherein: After the growth of the first multi-quantum well layer is completed, a first annealing treatment is performed on the surface, and the first annealing treatment includes: The temperature of the reaction chamber is maintained at 810°C to 1050°C, the growth pressure is maintained at 30 torr to 360 torr, and a mixed gas of N2 and H2 is introduced into the reaction chamber and maintained for 6s to 60s to complete the first operation; Stop introducing the N2 and H2 mixed gas to complete the second operation; The first operation and the second operation are alternately completed at least once to complete the first annealing treatment.

11. The method for preparing a Micro LED epitaxial wafer according to claim 9, wherein: After the third multi-quantum well layer is grown, a second annealing treatment is performed on the surface, and the second annealing treatment includes: The temperature of the reaction chamber is maintained at 810°C to 1050°C, the growth pressure is maintained at 30 torr to 360 torr, and a mixed gas of N2 and H2 is introduced into the reaction chamber and maintained for 9s to 90s to complete the third operation; Stop introducing the N2 and H2 mixed gas to complete the fourth operation; The third operation and the fourth operation are alternately completed at least once to complete the second annealing treatment.

12. A Micro LED chip, characterized in that: The Micro LED chip includes the Micro LED epitaxial wafer as described in any one of claims 1 to 8.

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